Run cifuzz for changes in ext/ (#2086)

.github/workflows/cifuzz.yml

diff --git a/.github/workflows/cifuzz.yml b/.github/workflows/cifuzz.yml
index 1dc65bd..d4f2c7a 100644
--- a/.github/workflows/cifuzz.yml
+++ b/.github/workflows/cifuzz.yml
@@ -3,6 +3,7 @@
   pull_request:
     paths:
       - 'include/**'
+      - 'ext/**'
       - 'src/**'
       - 'tests/gtest/**'
       - 'tests/oss-fuzz/**'